Simplify .net core web api design complexity

This is a design related problem.

I have a legacy application in asp.net webforms which have 3 kind of users: Admin, Customer and Provider, which access multiple services like Product, Account, Sale, Purchase etc. All these 3 users share same set of class libraries for services, logic and database until now. And the deployment is single for all 3 users.

Now we are migrating this into .net core web api + angular. And I am thinking about the options. Till now I have figured out this is the best for our application:

1. Create separate web api for Admin, Customer and Provider. Then for any changes in Admin, the deployment will not impact Customer. But the problem with this approach is the class libraries will be duplicated. Some common methods will be duplicated.

Is there any alternative/good approach for this?